James Sheehan, chief of Schneiderman's charities bureau, penned a letter Friday to an attorney for the Donald J. Trump Foundation, accusing the charity of failing to register with the attorney general's office, a necessary step to solicit big-money donations in New York.

The letter to the Trump Foundation's attorney was publicly released Monday by Schneiderman's office.

The foundation must "immediately cease soliciting contributions or engaging in any other fundraising activities in New York," according to Sheehan's letter.

"The failure to immediately discontinue solicitation and to file information and reports required under (state law) ... shall be deemed to be a continuing fraud upon the people of the state of New York," he wrote.

New York-based charities are required to register with Schneiderman's charities bureau before seeking funds. Once they're registered, those with annual revenues of more than $250,000 have to submit financial reports to Schneiderman that essentially serve as an audit.

Hope Hicks, a spokeswoman for Trump's campaign, said the campaign remains "very concerned about the political motives" behind Schneiderman's probe, but said the foundation "nevertheless intends to cooperate fully with the investigation."

"Because this is an ongoing legal matter, the Trump Foundation will not comment further at this time," she said. Schneiderman, a Democrat, has repeatedly clashed with Trump in recent years.

In 2013, Schneiderman filed a fraud suit against Trump, accusing his "Trump University" program of bilking its participants and falsely overstating the Manhattan real-estate mogul's involvement.

Trump, who had previously donated to Schneiderman's campaign, countered with a public-relations, creating a website touting the Trump University program and filing an ethics complaint against the attorney general.